| Re: !D.N_COLORS and !D.TABLE_SIZE [message #4174] |
Mon, 08 May 1995 00:00 |
rivers
Messages: 228
Registered: March 1991
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Senior Member |
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In article <8MAY199500395445@sorbet.gsfc.nasa.gov>, landsman@sorbet.gsfc.nasa.gov (Wayne Landsman (301)-286-3625) writes:
> Does someone know the difference in IDL between !D.N_COLORS ("the number of
> simultaneously available colors") and !D.TABLE_SIZE ("the number of color
> table indices")? When would they have different values? -- I haven't
> been able to find such a case. Which one should one use, for example, to
> decide how to scale an image to use the maximum number of colors?
We have an Imaging Technology frame grabber for which I have written an IDL
device driver. It has 12 bits per pixel (hence !D.N_COLORS=4096) but 16
separate output lookup tables, each of which is 256 entries long
(hence !D.TABLE_SIZE=256). One can either statically chose one of the output
color tables, or have the high-order 4 bits of the pixel chose the color tables
dynamically.
I can imagine that !D.N_COLORS might be different from !D.TABLE_SIZE for true
color X displays, but I have never used those so I don't know for sure.
____________________________________________________________
Mark Rivers (312) 702-2279 (office)
CARS (312) 702-9951 (secretary)
Univ. of Chicago (312) 702-5454 (FAX)
5640 S. Ellis Ave. (708) 922-0499 (home)
Chicago, IL 60637 rivers@cars3.uchicago.edu (Internet)
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